70 CONTEMPORARY SCIENCE 



Our first big experience was an attack at Vermelles. 

 The Germans put down a heavy barrage of these shells and 

 made an infantry attack. The concentration was great, 

 the gas went through the helmets, and the men even vom- 

 ited inside their helmets. But it is difficult to put down 

 a gas barrage, and there is danger that it will not be a 

 technical success. In the instance cited certain roads were 

 not cut off sufficiently, so that reinforcements got up. 

 This attack, however, opened our eyes to the fact that, as 

 in the case of gas clouds, concentration would be developed 

 so as to make it high enough to produce the required 

 effect under any circumstances. 



When the Germans started using highly poisonous 

 shells, which was at the Somme in 1916, they did not at- 

 tend to this sufficiently, although enormous numbers of 

 shell were used. The substance used was trichloromethyl- 

 chloro formate, but not in great strength. It had no de- 

 cided reaction on the eyes, hence the men were often 

 caugfat. 



The quantity of gas that can be sent over in shells is 

 small. The average weight in a shell is not more than 

 six pounds, whereas the German gas cylinders contain 40 

 pounds of gas. To put over the same amount of gas as 

 with gas clouds, say in five minutes per thousand yards of 

 front, would require a prohibitive number of guns and 

 shells. It becomes necessary to put the shells on definite 

 targets, and this, fortunately, the Germans did not 

 realize at the Somme, although they have found it out 

 since. 



The use of gas out of a projectile has a number of ad- 

 vantages over its use in a gas cloud. First, it is not so 

 dependent on the wind. Again, the gunners have their 

 ordinary job of shelling, and there is no such elaborate 

 and unwelcome organization to put into the front trenches 

 as is necessary for the cloud. Third, the targets are 

 picked with all the accuracy of artillery fire. Fourth, the 

 gas shells succeed with targets that are not accessible to 



